Method for etching a metal layer in a semiconductor device

ABSTRACT

A method for etching a metal layer on which an oxide-based ARC layer is coated in a semiconductor device comprises the step of performing a dry cleaning process by using a Cl 2 /CHF 3  based gas, after dry cleaning the ARC layer by using the oxide-based gas. As a result, the etching rates of the center area and the edge area are substantially same.

FIELD OF THE INVENTION

[0001] The present invention relates to a method for forming metal linesin a semiconductor device; and, more particularly, to a method forsimultaneously etching a metal layer throughout the entire surface of awafer or substrate without causing microloading.

BACKGROUND OF THE INVENTION

[0002] Recently, as a semiconductor device becomes highly integrated, ina process for fabricating a semiconductor device, metal lines of about0.25 μm or smaller in width are required. As a result, it is general touse a DUV (Deep Ultra Violet) photoresist film in forming the metallines.

[0003] As the photoresist film is sensitive to a reflectance of themetal lines, the reflectance should be decreased to form a non-defectivephotoresist pattern. For the reason, an oxide-based antireflectivecoating (“ARC”) layer coated on the metal lines is widely used.

[0004] However, when an in-situ etching process of the ARC layer isperformed in a metal etching chamber, functions of the device may bedeteriorated due to a microloading effect between a center area and anedge area of a wafer or substrate. The microloading effect becomes moreserious in a far edge area being away from the center area.

[0005] As an approach for decreasing the microloading effect, there hasbeen proposed a process for improving a uniformity of metal lines.However, such a process has a limitation in overcoming a difference inetching rate between areas of the wafer. The problem is closely relatedwith a deposition of polymers in the chamber. Especially, when a Si—Xbased ARC material is deposited in the chamber, such phenomenon becomesmore severe.

[0006]FIGS. 1A and 1B illustrate cross sectional views showing statesafter etching of an ARC layer 2 and after etching of metal layers 3 and5, respectively.

[0007] As shown in FIG. 1A, in etching the ARC layer 2, the metal layer3 in a center area of a wafer 4 is exposed earlier than in an edge areaof the wafer since the etching rate is higher at the center area than atthe edge area.

[0008] Also, referring to FIG. 1B, after etching of the metal layer 3,the TiN layer 5 in the edge area is exposed less than in the centerarea.

[0009] That is, in such a conventional process, the etching rate of theARC layer is greater in the center area than in the edge area so thatthe metal layer may be excessively etched and there may occur anunderetch in the edge area.

[0010] When comparing the etching rates in the far edge area and thecenter area on the basis of a 10 mm wafer edge exclusion, experimentalresults indicate that the etching rate difference between the edge areaand the center area is 1400 Å/min or more.

SUMMARY OF THE INVENTION

[0011] It is, therefore, an object of the present invention to provide amethod for simultaneously etching a metal layer wherein an etching ratedecrease in an edge area of a wafer is prevented by performing anadditional dry cleaning process using a fluorine-based gas to eliminatea Si—X based polymer deposited in a chamber, thereby minimizing amicroloading effect.

[0012] In accordance with a preferred embodiment of the presentinvention, there is provided a method for etching a metal layer on whichan oxide-based ARC layer is coated in a semiconductor device comprisingthe step of:

[0013] performing a dry cleaning process by using a Cl₂/CHF₃ based gas,after dry cleaning the ARC layer by using an oxide-based gas.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above and other objects and features of the present inventionwill become apparent from the following description of preferredembodiments, given in conjunction with the accompanying drawings, inwhich;

[0015]FIGS. 1A and 1B illustrate cross sectional views sequentiallyshowing a conventional process of etching a metal layer;

[0016]FIGS. 2A and 2B depict cross sectional views sequentially showinga process of etching a metal layer in accordance with a preferredembodiment of the present invention; and

[0017]FIG. 3 shows a graph of an etching rate comparison between theconventional method and the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A preferred embodiment of the present invention will now bedescribed in detail with reference to the accompanying drawings, whereinlike reference numerals appearing in the drawings represent like parts.

[0019]FIGS. 2A and 2B illustrate cross sectional views showing anetching process of an ARC layer 2 and an etching process of metal layersin accordance with the preferred embodiment of the present invention,respectively.

[0020] As shown in FIG. 2A, after the ARC layer 2 has been etched, thereis substantially no difference between the etching depths in a centerarea and an edge area of a wafer 4.

[0021] As a result, as shown in FIG. 2B, the metal layers 3 and 5 in thecenter area and the edge area can simultaneously be etched.

[0022] This process is carried out by using two steps as indicated inTable 1. TABLE 1 Pressure Source Bias O₂ Cl₂ CHF₃ (mTorr) power (W)power (W) (sccm) (sccm) (sccm) First 8˜50 500˜1200 0˜10 300˜500 0 0 stepSecond 8˜50 500˜1200 0˜10 0 100˜200 5˜30 step

[0023] As in the second step of Table 1, in order to eliminate polymers,e.g., AlCl_(x) and Si—X, which are byproducts deposited in a metaletching chamber, a Cl₂/CHF₃ based dry cleaning process is employed; and,therefore, the process results as shown in FIGS. 2A and 2B are obtained.

[0024] At this time, the process is preferably performed for about 5seconds to about 30 seconds.

[0025]FIG. 3 shows a graph of an etching rate comparison between aconventional process and the process of the present invention.

[0026] As shown in FIG. 3, because a microloading effect of the etchingrate in the present invention is less than that of the conventionalmethod, the etching rates of the center area and the edge area aresubstantially same.

[0027] Here, in the edge area, the data of FIG. 3 were obtained on thebasis of a 10 mm wafer-edge exclusion.

[0028] In accordance with the present invention, the etching rate in theedge area is not decreased, because the etching process at the edge areais not hindered.

[0029] Experimentally, when comparing the etching rates in the centerarea and the far edge area on the basis of the 10 mm wafer-edgeexclusion, there is substantially no difference therebetween, therebypreventing the underetch which may occur in the far edge area.

[0030] As a result, the reliability of the metal etching process isimproved, and in the etching process of the metal layers 3 and 5 havingthe ARC layer 2 thereon, a seasoning effect which may occur by a drycleaning is reduced.

[0031] While the invention has been shown and described with respect tothe preferred embodiments, it will be understood by those skilled in theart that various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

What is claimed is:
 1. A method for etching a metal layer on which anoxide-based ARC layer is coated in a semiconductor device comprising thestep of: performing a dry cleaning process by using a Cl₂/CHF₃ basedgas, after dry cleaning the ARC layer by using an oxide-based gas. 2.The method of claim 1, wherein a flow rate of the Cl₂ based gas rangesfrom about 100 sccm to about 200 sccm.
 3. The method of claim 1, whereina flow rate of the CHF₃ based gas ranges from about 5 sccm to about 30sccm.
 4. The method of claim 1, wherein a pressure of the dry cleaningprocess ranges from about 8 mTorr to about 50 mTorr.
 5. The method ofclaim 1, wherein a source power of the dry cleaning process ranges fromabout 500 W to about 1200 W.
 6. The method of claim 1, wherein a biaspower of the dry cleaning process ranges from about 0 W to about 10 W.7. The method of claim 1, wherein the dry cleaning process is performedfor about 5 seconds to about 30 seconds.